The present invention relates to an expandable fiberoptic catheter and a method of transmitting laser energy through a catheter, especially for intraluminal surgical procedures such as laser angioplasty, laser atherectomy, laser thrombolysis, laser lithotripsy and the like.
It is well known that laser energy may be transmitted through a plurality of optical fibers housed in a relatively flexible tubular catheter which may be inserted into a body lumen, such as a blood vessel, ureter, fallopian tube, cerebral artery, etc., to remove obstructions in the lumen. Our prior U.S. Pat. Nos. 4,784,132; 4,800,876; 4,848,336 and 5,041,108, the disclosures of which are incorporated herein by reference, describe apparatus, including catheters, and methods that may be used for the intraluminal transmission of laser energy through a plurality of optical fibers to remove obstructions in a body lumen. U.S. Pat. No. 5,250,045 discloses another type of catheter that may also be used for the intraluminal transmission of laser energy. Such catheters as are in use at the present time for laser angioplasty and similar procedures typically have a central passage or tube which receives a guide wire inserted into the body lumen prior to introduction of the catheter.
Typical of commercially available laser angioplasty equipment are the CVX-300 Excimer Laser Angioplasty System and Extreme and Vitesse catheters manufactured by The Spectranetics Corporation of Colorado Springs, Colo. and the DYMER 200+ Excimer Laser Angioplasty System and LITVACK catheters manufactured by Advanced Interventional Systems, Inc. of Irvine, Calif.
One common drawback of most catheters which house a plurality of optical fibers, especially those for use in removing obstruction from small diameter body lumens, such as blood vessels, is that the longitudinal axes of the fibers are spaced radially inwardly from the inner wall of the lumen to a significant degree. Such spacing includes, for example, the thickness of the catheter sheath and any cladding on the optical fibers as well as the radial spacing between the outside periphery of the catheter and the inner lumen wall. Typically, the outermost diameter of the catheter is substantially less than the diameter of the lumen so that the catheter can pass through the lumen without difficulty. Where the laser energy is used to vaporize an obstruction in the body lumen such radial spacing of the optical fibers from the lumen wall results in drilling one or several relatively small diameter holes in the central area of the obstruction thereby leaving a substantial annular portion of the obstruction against the lumen wall.
In the case of laser angioplasty, it has been a common practice to perform a subsequent adjunctive balloon angioplasty procedure in the hope of compacting to some extent the annular portion of the obstruction that remains after the laser angioplasty procedure has been completed. Not only is the balloon angioplasty procedure a time-consuming and expensive adjunct to the laser angioplasty procedure, it adds significantly to the possibility of mechanical damage or trauma to the vessel wall and, if anything, results in a greater likelihood of restenosis than with laser angioplasty alone.
It would be desirable therefore to provide a catheter designed to enable the laser energy to impinge upon and remove or vaporize an obstruction in a body lumen as close as possible to the wall of the body lumen without thermal or mechanical damage to the lumen wall itself.
It has been suggested that inflatable balloons might be used to move the optical fibers radially inwardly and outwardly relative to the longitudinal axis of the catheter. Our aforementioned patents disclose a catheter in which an array of four optical fibers is moved along a radial plane by a balloon. U.S. Pat. Nos. 4,790,310; 5,066,292; 5,176,674; and 5,203,779 all disclose catheters which can transmit laser energy for use in laser angioplasty in which a balloon or other inflatable component is used to alter the positions of the optical fibers housed in the catheter. However, some of the prior art catheters have certain drawbacks that make their use less than optimum and in some cases potentially dangerous. For example, the aforesaid U.S. Pat. Nos. 4,790,310; 5,066,292; and 5,203,799 position the axes of the optical fibers at an outwardly diverging angle relative to the axis of the catheter. Such orientation of the optical fibers presents the danger that the laser energy will impinge upon the wall of the lumen and possibly vaporize or perforate the lumen wall. U.S. Pat. Nos. 5,176,674 and 5,203,779 teach embedding the optical fibers in the wall of the inflatable member which requires the wall to be of a greater thickness than necessary to contain the inflating fluid and therefore more difficult to inflate.